1. Field of the invention
The present invention relates to a tool holder in an automatic tool change means in a tool machine, and especially to a tool holder of a hollow taper shank in a tool machine.
2. Description of the prior art
In the prior art synthetic tool machine, BT knifes is a primary cutting means. However, due to the improvement of technology and the requirement of high speed rotation, the rotary speed of the primary shaft of a tool machine will improve continuously. The conventional BT knife with lower clamping force is not suitable. In order to prevent the fall of the knife in high speed rotation, a new HSK short knife having two resisting surfaces for improving clamping force is developed, which is so called hollow taper shank system. In order to meet with the polarity of the HSK short knife, the knife storage of the tool machine must be changed for suiting the HSK short knife.
The prior art tool holders have two types for meeting the requirement of the HSK short knife in the tool machine, as shown in FIGS. 5, 6, 7 and 8.
The prior art tool holder of the HSK short knife in FIGS. 5 and 6 is a tool holder using an elastic steel piece. At first, the shape of the elastic steel piece 80 is punched to have a shape matching the inner space of a knife 81. Then, the elastic force of the elastic steel piece 80 serves to prevent the tool holder 82 from falling down. However, such structure has the following defects:
1) The elastic steel piece 80 has an elastic structure. The interior of the knife 81 is a round hole 83. There are only 12 contact points. Moreover, since the elastic force of the elastic steel piece 80 cannot be well controlled, the knife 81 cannot be fixed effectively. Thus, as the knife storage is operated, the knife 81 may possibly release due to the weight thereof to make a hazard.
2) Six piece elastic steel pieces 80 easily have errors from assembly so that the contact points of the steel pieces 80 are not in the same plane so that in operation, the knife 81 is possibly released to induce an accident.
As shown in FIGS. 7 and 8, a means with a spring and four steel balls is illustrated. In this means, the steel balls 90 are ejected by a spring 91 so as to be fixed, however such design has the following defect:
1) The spindle 93 of the knife 92 and the spring seat 94 have a small space. A proper spring 91 is difficult to be found. If it is found, the elastic force is also smaller, so that the clamping force between the spring 91 and the knife 92 is not enough. Thus, the knife easily falls.
2) Since the steel ball seat 95 is necessary to be mounted separately for installing the steel balls 90 onto the spring 91, some inconvenience is induced.
3) Since the volume of the steel ball seat 95 is too large, interruptions will occur with the injecting hole for cutting liquid. Therefore, it is only suitable to be used in a knife 92 without an inject hole.
Accordingly, the primary object of the present invention is to provide a tool holder of hollow taper shank in a tool machine, wherein as the tool holder receives a knife, steel balls will exert an outward action force from a pushing block and a spring, so that the steel balls formed with an outwards acting force will firmly secure the knife without releasing.
Another object of the present invention is to provide a tool holder of hollow taper shank in tool machine, since the tool holder is installed with a positioning confining block with respect to the knife, thus, the knife only inserts into the tool holder unidirectionally so as to prevent an improper rotation of the knife as it is buckled in the tool holder.
A further object of the present invention is to provide a tool holder of hollow taper shank in tool machine, it can be assembled easily and rapidly for increasing the buckling force to a hollow short knife (for simplifying, it is called as an HSK short knife hereafter).
A yet object of the present invention is to provide a tool holder of hollow taper shank in tool machine. The HSK short knife is installed with an injecting hole for cutting liquid or without an injecting hole.
A tool holder of hollow taper shank in tool machine is disclosed, wherein a resisting block supported by a spring is received with a tool holder. As the short knife is disposed within the tool holder, the elastic force of the spring can be overcome. At first, the plurality of steel balls and the resisting block are pushed inversely until the front edge of a wider portion of the short knife passes through the steel ball. Now, the spring will release the energy of elastic deformation so as to enforce the resisting block to return to the original position forwards and outwards. Thereby, the knife can be firmly secured.